Enantioselective Intramolecular Nicholas Reaction Catalyzed by Chiral Phosphoric Acid: Enantioconvergent Synthesis of Seven-Membered Cyclic Ethers from Racemic Diols.

An enantioconvergent intramolecular Nicholas reaction of racemic diols was developed using BINOL- and SPINOL-derived phosphoric acids as the chiral Brønsted acid catalyst. The developed reaction features an efficient approach to the synthesis of seven-membered cyclic ethers in a highly enantioselective manner. Further derivatization of the enantioenriched cyclic ethers, initiated by the de-complexation of the dicobalt species, afforded densely functionalized cyclic ethers having an unsaturated diester moiety without loss of enantiomeric excess.